It is common for an irrigation sprinkler to include a pressure regulating device, such as a valve, in order to regulate a downstream fluid pressure in the sprinkler housing or case prior to the outlet nozzle. Maintaining a consistent fluid pressure at the nozzle outlet ensures optimum performance and efficiency of the fluid stream or spray. An undesired decrease in fluid pressure below a predetermined range often forms a fluid stream or spray with less energy, which may be susceptible to wind effects. On the other hand, an undesired increase in fluid pressure above a predetermined range may result in misting, fogging, or unwanted fluid trajectories.
For example, a gear-driven rotor often includes a pressure regulating valve within an inlet to the rotor housing. The valve includes a control portion that communicates with a pressure controller, which measures fluid pressure in the rotor housing downstream of the valve. If the pressure exceeds a predetermined set-point, the pressure controller causes the valve to close. If the pressure drops below a predetermined set-point, the pressure controller causes the valve to open. In this manner, the pressure within the housing can be maintained within a predetermined range for optimal nozzle performance.
In general, pressure regulating valves commonly consist of two basic types depending on the flow rate through the sprinkler housing: high-flow or low-flow valves. For instance, high-flow valves are suitable to maintain desired case pressures with fluid flow up to about 16 gallons per minute or higher. Low-flow valves, on the other hand, are generally suitable to maintain case pressures with fluid flow as low as about 1.3 gallons per minute. For purposes of this application, high flow and low flow can mean any range of flow rates. The valves can be designed with a sealing poppet connected to a piston, and an outlet orifice suitable for its optimum flow range to achieve the desired downstream pressures. In many cases, the piston utilizes a flat gasket in order to more efficiently seal the piston against the valve seat when the valve is closed.
Unfortunately, pressure regulating valves are generally not robust enough to be useful outside of their designed pressure and flow set points. For instance, the orifice size of the low flow valve is generally too small for effective use in an irrigation sprinkler device optimized for high flow rates because the small orifice size would cause a very large pressure drop across the valve so the case pressure would be undesirably too low for effective outlet nozzle performance.
On the other hand, the high flow valve has a larger inlet orifice reducing the pressure drop across the valve, but at low flow rates, the valve exhibits an undesired behavior where the valve is constantly opening and closing because the downstream pressure can not be maintained. For instance, a decrease in flow rate results in a corresponding decrease in the pressure drop across the valve. As a result, when the flow rate is sufficiently low, the pressure drop across the valve is decreased such that the case pressure downstream of the valve is above the desired set-point; therefore, the valve closes. As the case pressure again drops to below the desired set-point range, the valve again opens and sufficient flow at a low pressure drop rushes past the valve so that the desired case pressure is again quickly exceeded. The cycle is then repeated. Such repeated opening and closing of the valve is a behavior commonly known as “hunting.” This undesired behavior results in poor nozzle performance, unnecessary wear on the valve components, and inefficient irrigation.
As described above, to avoid such valve behavior, multiple pressure regulating valves are designed to operate in predetermined pressure and flow ranges. However, multiple valve designs require increased manufacturing costs due to multiple parts, increased tooling, and large inventories. Moreover, once installed in an irrigation system, if the base pressures or flow rates vary beyond the valve's optimum pressure and flow ranges, the valve may fall outside its desired performance range and exhibit the undesired behaviors described above.
Accordingly, an irrigation pressure regulating device is desired that effectively regulates pressure over a wide flow and pressure range without the undesired behaviors of current pressure regulating valves.